Solid state image pickup device and camera

ABSTRACT

A solid state image pickup device which can prevent color mixture by using a layout of a capacitor region provided separately from a floating diffusion region and a camera using such a device are provided. A photodiode region is a rectangular region including a photodiode. A capacitor region includes a carrier holding unit and is arranged on one side of the rectangle of the photodiode region as a region having a side longer than the one side. In a MOS unit region, an output unit region including an output unit having a side longer than the other side which crosses the one side of the rectangle of the photodiode region is arranged on the other side. A gate region and the FD region are arranged between the photodiode region and the capacitor region.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a solid state image pickup device and a cameraand, more particularly, is suitable for use in a CMOS area sensor.

2. Related Background Art

In recent years, the CMOS area sensor in which a photodiode and a MOStransistor are formed as one chip is used as a solid state image pickupdevice. The CMOS area sensor has such advantages that electric powerconsumption is smaller, a driving electric power is smaller, and ahigher processing speed can be realized as compared with those of a CCD.The general CMOS area sensor is constructed by forming a plurality ofpixels in a matrix shape, in which each pixel has: a photodiode; afloating diffusion (hereinbelow, also abbreviated to FD as necessary)region; a transfer transistor for transferring carriers from thephotodiode to the FD region; and a reset transistor for resetting the FDregion to a predetermined electric potential.

A technique regarding the CMOS area sensor whose dynamic range iswidened has been examined (for example, refer to Shigetoshi Sugawa, andother five persons, “A 100 db Dynamic Range CMOS Image Sensor Using aLateral Overflow Integration Capacitor”, ISSCC2005/SESSION19/IMAGES/19.4, DIGEST OF TECHNICAL PAPERS, 2005 IEEEInternational Solid-State Circuit Conference, Feb. 8, 2005, p 352-353,603). According to the CMOS area sensor in the above non-PatentDocument, in each pixel, further, a capacitor region whose capacitanceis larger than that of the FD is formed, one terminal of the capacitorregion is connected to the FD through a switch, and the other terminalof the capacitor region is connected to the ground. Thus, when carriersoverflow from the photodiode by strong light, the overflowed carriersare held into the capacitor region, thereby enabling a signalcorresponding to a quantity of overflowed carriers to be outputted andwidening the dynamic range.

In the CMOS area sensor, however, there is a problem that a colormixture with the adjacent pixel occurs irrespective of the presence orabsence of the widening function of the dynamic range mentioned above.FIGS. 8A and 8B are diagrams showing a mechanism of the occurrence ofthe color mixture according to conventional pixel layouts. In FIG. 8A, atransfer unit 502 and a MOS unit 503 are arranged under a photodiode501. When the pixels having such a layout are arranged, even if a deviceseparating region is provided between the pixels, there is a case wherethe color mixture cannot be avoided. In the case of FIG. 8A, since theMOS unit 503 is arranged in the vertical direction or the like, adistance between the photodiodes of the adjacent pixels is larger thanthat of the adjacent pixels in the lateral direction. However, forexample, as shown in FIG. 8A, photodiodes 501 and 504 are arranged inthe lateral direction so as to sandwich only the device separatingregion. There is, consequently, such a problem that the color mixtureoccurs because the carriers which have been photoelectrically convertedin a deep layer portion of silicon leak or light or the like which hasobliquely entered and has been reflected by an aluminum layer or thelike enters the adjacent photodiode.

As shown in FIG. 8B, a transfer unit 512 and a floating diffusion region513 are provided on the right side of a photodiode 511 and the MOS unitis provided under the photodiode 511. Owing to such a layout, although adistance between the photodiode 511 and a photodiode 521 of the pixelwhich is adjacent on the right side of the photodiode 511 is larger thanthat in the case of FIG. 8A, since a distance between the floatingdiffusion region 513 and the photodiode 521 is small, there is a problemthat the carriers leak into the floating diffusion region 513 and thecolor mixture occurs.

According to the layout disclosed in the above non-Patent Document,since it is necessary to set a large capacitor region, it exercises alarge influence on the problem of the color mixture in dependence on thelayout.

SUMMARY OF THE INVENTION

The invention is made in consideration of the foregoing circumstancesand it is an object of the invention to provide a solid state imagepickup device which can prevent color mixture by effectively using alayout of a capacitor region provided separately from a floatingdiffusion region and to provide a camera using such a solid state imagepickup device.

The invention is made to solve the foregoing problem and according tothe invention, there is provided a solid state image pickup deviceconstructed by arranging unit pixels in a matrix shape, in which eachunit pixel comprises: a photoelectric conversion unit where carriers aregenerated by incident light; a transfer unit adapted to transfer thecarriers; a floating diffusion region where the carriers are transferredby the transfer unit; a carrier holding unit adapted to accumulate thecarriers overflowed from the photoelectric conversion unit; and anoutput unit adapted to output a signal corresponding to the carrierstransferred to the floating diffusion region,

wherein one of the carrier holding unit and the output unit is providedbetween the photoelectric conversion unit included in the first pixeland the photoelectric conversion unit included in the second pixeladjacent to the first pixel in the row direction, and

the other one of the carrier holding unit and the output unit isprovided between the photoelectric conversion unit included in the firstpixel and the photoelectric conversion unit included in the third pixeladjacent to the first pixel in the column direction.

In one embodiment, the transfer unit and the floating diffusion regionmay be arranged between the photoelectric conversion unit and thecarrier holding unit.

According to the invention, there is provided a camera comprising: thesolid state image pickup device; a lens adapted to focus an opticalimage onto the solid state image pickup device; and a diaphragm adaptedto vary a quantity of light which passes through the lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams showing an example of a circuitconstruction of each pixel of a solid state image pickup deviceaccording to an embodiment and a schematic example of a layoutconstruction;

FIG. 2 is a timing chart showing an example of the operation of a pixelcircuit of the solid state image pickup device shown in FIG. 1A;

FIG. 3 is a diagram showing an example of a more detailed layout of theschematic layout shown in FIG. 1B;

FIG. 4 is a diagram showing an example of a more detailed layout of theschematic layout shown in FIG. 1B and shows the layout different fromFIG. 3;

FIG. 5 is a diagram showing an example of a more detailed layout of theschematic layout shown in FIG. 1B and shows the layout different fromFIG. 4;

FIG. 6 is a block diagram showing the case where the solid state imagepickup device in each embodiment mentioned above is applied to a “stillcamera”;

FIG. 7 is a block diagram showing the case where the solid state imagepickup device in each embodiment mentioned above is applied to a “videocamera”; and

FIGS. 8A and 8B are diagrams showing a mechanism of the occurrence ofcolor mixture according to conventional pixel layouts.

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention will be described hereinbelowwith reference to the drawings.

First Embodiment

First, a solid state image pickup device (CMOS area sensor) in the firstembodiment of the invention will be described. FIG. 1A is a diagramshowing an example of a circuit construction of each pixel of the solidstate image pickup device in the embodiment. FIG. 1B is a diagramshowing a schematic example of a layout construction of each pixel ofthe solid state image pickup device in the embodiment.

First, the circuit construction of each pixel will be described withreference to FIG. 1A.

As shown in FIG. 1A, each pixel of the solid state image pickup devicein the embodiment comprises: a photodiode 10; a first transfer MOStransistor 11; a reset MOS transistor 12; a second transfer MOStransistor 13; a carrier holding unit (capacitor) 14; a source-followerMOS transistor 15; and a selection MOS transistor 16. The pixels of thesolid state image pickup device are arranged in a two-dimensional matrixshape of (a plurality of rows×a plurality of columns).

The photodiode 10 accumulates carriers generated by the incident light.The photodiode 10 is connected to an FD 17 through the first transferMOS transistor 11. The FD 17 has a layout construction also serving as adrain terminal of the first transfer MOS transistor 11 and can hold thecarriers which are transferred from the photodiode 10 through the firsttransfer MOS transistor 11. The FD 17 is mutually connected to a drainterminal of the reset MOS transistor 12, a gate terminal of thesource-follower MOS transistor 15, and a drain terminal of the secondtransfer MOS transistor 13.

A source terminal of the second transfer MOS transistor 13 is connectedto the ground through the carrier holding unit 14. Source terminals ofthe reset MOS transistor 12 and the source-follower MOS transistor 15are connected to a power source line for supplying, for example, a powervoltage VDD. A drain terminal of the source-follower MOS transistor 15is mutually connected to a source terminal of the selection MOStransistor 16. A signal which changes in accordance with an amount ofcarriers transferred to the FD 17 is outputted from the transistor 16.As a circuit construction shown in FIG. 1A described above, aconstruction similar to that of each pixel of the solid state imagepickup device described in the related background art (non-PatentDocument) can be used.

Each of the first transfer MOS transistor 11, reset MOS transistor 12,second transfer MOS transistor 13, and selection MOS transistor 16 isON/OFF controlled by a control signal which is supplied to a gateterminal of each of those transistors. When the control signal of thehigh level is supplied to the gate terminal, each of the first transferMOS transistor 11, reset MOS transistor 12, second transfer MOStransistor 13, and selection MOS transistor 16 is turned on (madeconductive). When control signal of the low level is supplied to thegate terminal, each of those transistors is turned off (madenonconductive).

Specifically speaking, as shown in FIG. 1A, a control signal TX issupplied to the gate terminal of the first transfer MOS transistor 11, acontrol signal SW is supplied to the gate terminal of the secondtransfer MOS transistor 13, a control signal SEL is supplied to the gateterminal of the selection MOS transistor 16, and control signal RES issupplied to the gate terminal of the reset MOS transistor 12,respectively.

The control signal TX is a control signal to transfer the carriersaccumulated by the photoelectric conversion in the photodiode 10 to theFD 17. The control signal SW is a control signal to connect the FD 17 tothe carrier holding unit 14. The control signal SEL is a control signalto select the pixel. The control signal RES is a control signal to resetan electric potential of the FD 17 to the power voltage VDD (forexample, +5V).

An example of the operation of the pixel circuit of the solid stateimage pickup device shown in FIG. 1A will now be described. FIG. 2 is atiming chart showing the example of the operation of the pixel circuitof the solid state image pickup device shown in FIG. 1A. As shown inFIG. 2, since the control signals RES, SEL, TX, and SW are supplied, thepixel of FIG. 1A outputs the carriers, as a pixel signal, which havebeen photoelectrically converted in the photodiode 10 for a period oftime corresponding to the control.

First, when the control signal RES is turned on at time t1 in the statewhere the control signals SW and SEL are ON and other control signalsare OFF, the electric potentials of the FD 17 and the carrier holdingunit 14 are reset to the power potential VDD. Since the control signalRES is turned off at time t2, the resetting operation is completed.

Subsequently, the control signal SEL is turned off at time t3. Thus, theaccumulation of the carriers is started in the photodiode 10. Since thecontrol signal SW is ON during the accumulation, for example, in thecase where the photodiode 10 receives strong light and overflows and thecarriers overflow to the FD 17, those carriers are accumulated in bothof the FD 17 and the carrier holding unit 14.

Subsequently, the reading process of the pixel signal according to thecarriers which have been photoelectrically converted in the photodiode10 is executed. Specifically speaking, the control signal SW is turnedoff at time t4 and the control signal SEL is turned on at time t4. Thus,the FD 17 is disconnected from the carrier holding unit 14.

Subsequently, the control signal RES is turned on at time t5. Thus, forexample, even if the carriers have been accumulated in the FD 17 due tothe overflow of the photodiode 10, the electric potential of the FD 17is reset to the power voltage VDD. Since the second transfer MOStransistor 13 is turned off by the turn-off of the control signal SW,the carrier holding unit 14 is not reset. That is, if the overflowedcarriers exist, the carrier holding unit 14 continues to hold them. Thecontrol signal RES is turned off after a predetermined period from timet5 (time earlier than time t6, which will be explained hereinbelow).

Subsequently, since the control signal TX is turned on at time t6, thefirst transfer MOS transistor 11 is turned on and the carriersaccumulated in the photodiode 10 are transferred to the FD 17. Thus, theoutput signal of the source-follower MOS transistor 15 according to thecarriers which have been transferred to the FD 17 and held is outputtedas a pixel signal.

Subsequently, the reading process of the pixel signal according to theoverflowed carriers to widen the dynamic range is executed. If nooverflow occurs in the photodiode 10, the carriers are not held in thecarrier holding unit 14. However, explanation will be made here on theassumption that the carriers overflowed by the overflow have been heldin the carrier holding unit 14.

Specifically speaking, when the control signal SW is turned on at timet7 and the control signal TX is turned on at time t8, the carriers whichhave overflowed by the overflow and have been held in the carrierholding unit 14 and the carriers held in the FD 17 are added. Thus, theoutput signal of the source-follower MOS transistor 15.according to theadded carriers is outputted as a pixel signal. Subsequently, when thecontrol signal RES is turned on at time t9, the electric potentials ofthe FD 17 and the carrier holding unit 14 are reset to the powerpotential VDD.

Since the pixel signal can be outputted on the basis of an amount ofoverflowed carriers which have been held in the carrier holding unit 14owing to the circuit construction of FIG. 1A as described above, thedynamic range can be widened. It is preferable that the carrier holdingunit 14 has a capacitance larger than that of the FD 17. Therefore, anarea of the carrier holding unit 14 which occupies in the layout of eachcircuit element of the pixel is the second largest area next to the areaof the photodiode 10.

An example of the layout of the circuit shown in FIG. 1A will now bedescribed with reference to FIG. 1B. According to the layout example ofthe embodiment shown in FIG. 1B, the color mixture (It is referred as acrosstalk in the case of a monochromatic CMOS area sensor.) between theadjacent pixels can be reduced and a feature of the embodiment is shown.Component elements shown at reference numerals 101 to 103 in FIG. 1Acorrespond to those in FIG. 1B. That is, a photodiode region 101 is aregion including the photodiode 10. A capacitor region 102 is a regionincluding the carrier holding unit 14. A MOS unit region 103 is a regionincluding the reset MOS transistor 12, source-follower MOS transistor15, and selection MOS transistor 16. There is also a case where the MOSunit region 103 includes the second transfer MOS transistor 13 althoughits details will be explained hereinafter. It is assumed that thedirection of the capacitor regions when they are seen from thephotoelectric conversion unit is set to the column direction and thedirection of the MOS unit regions is set to the row direction. However,the invention is not limited to them but the row direction and thecolumn direction may be also exchanged.

A gate region 11 a is a gate region constructing the gate terminal ofthe first transfer MOS transistor 11. An FD region 104 is a regionconstructing the FD 17 and is also a region constructing the drainterminal of the first transfer MOS transistor 11.

It is a feature of the layout shown in FIG. 1B and described above thatif the photodiode region 101 is a rectangle (may be also anapproximately rectangular), the capacitor region 102 is arranged on oneside of the rectangle and the MOS unit region 103 is arranged on anotherside (which crosses the above one side) of the rectangle. It isdesirable that each of the capacitor region 102 and the MOS unit region103 is equal to or longer than one corresponding side of the photodioderegion 101. In the capacitor region 102, it is possible to assure acapacitor by forming an n-type region or the like into a siliconsubstrate. However, preferably, a capacitor is formed on an oxide filmwithout forming a conductive region such as an n-type region or the likeinto the silicon substrate.

A forming method of the capacitor region 102 will be described. To formthe capacitor in the capacitor region 102, for example, it is consideredto form a MOS capacitor or a double-layer POL (polysilicon) capacitor.Particularly, in the embodiment, it is preferable to use thedouble-layer POL capacitor in which there is no need to form a diffusionlayer into the silicon substrate and which is constructed by formingdouble polysilicon layers on an oxide film or an LOCOS (Local Oxidationof Silicon) so as to sandwich a dielectric film. Thus, it is possible toprevent that the carriers from the adjacent pixel serving as a cause ofthe color mixture pass through the silicon substrate of the capacitorregion 102.

It is also preferable to form the MOS capacitor in a part in thecapacitor region 102. The MOS capacitor is a capacitor which isconstructed by a method whereby the diffusion layer is formed on thesilicon substrate, the dielectric film is formed on the diffusion layer,and a polysilicon layer is formed on the dielectric film.

The MOS capacitor and the double-layer POL capacitor can be also formedin the same region. By such a structure, a capacitance of the carrierholding unit 14 which is formed in the capacitor region 102 can beincreased. Accordingly, an example of a construction in which the MOScapacitor and the double-layer POL capacitor are formed in the sameregion will be described hereinbelow.

First, a diffusion layer is formed in the surface region of a P well bydoping (adding) n-type impurities therein. A capacitor (junctioncapacitor) is formed between the diffusion layer serving as an n-typeregion (region containing the n-type impurities) and the P well servingas a p-type region (region containing p-type impurities) and thecarriers can be accumulated in the capacitor.

A first dielectric film is formed on the diffusion layer. In the casewhere the periphery of the diffusion layer is element-isolated by aninsulating layer such as LOCOS or the like, the first dielectric filmcan be also formed on the insulating layer.

A first polysilicon layer is formed on the first dielectric film. Thefirst dielectric film is connected to the power potential VDD or theground potential. Subsequently, a second dielectric film is formed onthe first polysilicon layer. A second polysilicon layer is formed on thesecond dielectric film.

As mentioned above, in the embodiment, a first capacitor is formed bythe diffusion layer serving as an n-type region and the P well servingas a p-type region. A second capacitor is formed by the diffusion layerserving as an n-type region, the first polysilicon layer, and the firstdielectric film. Further, a third capacitor is formed by the firstpolysilicon layer, the second polysilicon layer, and the seconddielectric film. That is, to form the first to third capacitors, the Pwell, diffusion layer, first dielectric film, first polysilicon layer,second dielectric film, and second polysilicon layer are laminated.

The first polysilicon layer and the second polysilicon layer have theconductivity because the impurities are doped (added) therein. It issufficient that the first polysilicon layer and the second polysiliconlayer are made of a material having the conductivity and it is notalways necessary to use polysilicon. Each of the first and seconddielectric films is formed by laminating, for example, an SiO₂ film andan SiN₂ film. The thinner the first and second dielectric films are, thelarger its capacitance is. Therefore, it is desirable to decrease thethickness of each of the first and second dielectric films within alimit range where the insulation of the first and second dielectricfilms is not broken or deteriorated by the applied voltage.

In the case of forming the diffusion layer (n-type region) into thesilicon substrate, it is not formed around the side (left side in FIG.1B) which faces a boundary with the adjacent pixel, thereby enabling astructure which is strong against the color mixture to be realized. Adegree of distance to the side which faces the boundary where thediffusion layer (n-type region) is formed is determined in considerationof both of the specifications for prevention of the color mixture andthe specifications of the capacitance which is necessary for the carrierholding unit 14.

By using the layout as mentioned above, the capacitor region 102 or theMOS unit region 103 is certainly arranged between the photodiode regions101 of the pixels which are neighboring in the vertical direction or thepixels which are neighboring in the lateral direction. That is, thephotodiode region 101 serving as a target where the carriers of thecolor mixture enter is arranged at a remote position from the photodioderegion 101 of another adjacent pixel. The FD region 104 serving as atarget where the carriers of the color mixture enter is also arranged ata remote position from the photodiode region 101 or FD region 104 ofanother pixel. The capacitor region 102 has the structure which isstrong against the color mixture as mentioned above. As for the MOS unitregion 103, the carriers which become a cause of the color mixture canbe absorbed in the drain region. Consequently, the color mixture can bereduced more than the case of the conventional one by using the layoutof the capacitor region 102 provided separately from the FD region 104.

By substantially equalizing a length of one side of the photodioderegion 101 in which it is necessary to assure the largest area with thatof one side of the capacitor region 102 in which it is necessary toassure the second largest area, the efficient layout is realized. Byarranging the FD region 104 between the photodiode region 101 and thecapacitor region 102, the efficient layout according to a transfer pathof the carriers shown by an arrow in FIG. 1B can be also realized.

An example of a more detailed layout of the schematic layout shown inFIG. 1B will now be described.

FIG. 3 is a diagram showing the example of the more detailed layout ofthe schematic layout shown in FIG. 1B. As shown in FIG. 3, four gateregions are formed in the MOS unit region 103. That is, a gate regionSEL including the gate terminal of the selection MOS transistor 16, agate region SF including the gate terminal of the source-follower MOStransistor 15, a gate region RES including the gate terminal of thereset MOS transistor 12, and a gate region SW including the gateterminal of the second transfer MOS transistor 13 are arranged from theleft side. The foregoing control signals SEL, RES, and SW are inputtedto the gate regions SEL, RES, and SW.

A region on the left side of the gate region SEL is a drain regionconstructing a drain terminal of the selection MOS transistor 16 and acontact 305 to output the pixel signal to the outside is arranged inthis drain region. A region between the gate regions SF and RES is asource region where the source terminal of the source-follower MOStransistor 15 and the source terminal of the reset MOS transistor 12 areused in common and a contact 304 to connect to the power line forsupplying the power potential VDD is arranged in this source region.

In an alternating example, the FD region 104 may be arranged between thephotodiode region 101 and the MOS unit region 103. It is to beunderstood that the MOS unit region operates as an output unit adaptedto output a signal corresponding to a signal transferred to the floatingdiffusion region.

A region between the gate regions RES and SW is a drain region where thedrain terminal of the reset MOS transistor 12 and the drain terminal ofthe second transfer MOS transistor 13 are used in common and a contact303 to connect to the FD region 104 is arranged in this drain region. Aregion on the right side of the gate region SW is a source regionconstructing the source terminal of the second transfer MOS transistor13 and a contact 302 to connect to the capacitor region 102 is arrangedin this source region. A contact 301 to connect to the contact 303 isarranged in the FD region 104.

As shown in FIG. 3, by providing the drain region which uses in commonthe drain terminal of the reset MOS transistor 12 and the drain terminalof the second transfer MOS transistor 13, it is possible to prevent thatthe capacitance of the FD 17 is set to be too large. It is necessary toproperly set the value of the capacitance of the FD 17. If it is set tobe too large, a deterioration in gain occurs upon reading of thecarriers, to deteriorate a signal to noise ratio. Therefore, among thethree drain regions of the first transfer MOS transistor 11, reset MOStransistor 12, and second transfer MOS transistor 13 which exert aninfluence on the capacitance of the FD 17, the two drain regions areused in common, thereby suppressing the capacitance of the FD 17 lowerthan that in the case where the drain regions of the first transfer MOStransistor 11, reset MOS transistor 12, and second transfer MOStransistor 13 are formed by one region as shown in, for example, FIG. 5,which will be explained hereinafter.

A layout example different from that in FIG. 3 will now be described.FIG. 4 is a diagram showing an example of a more detailed layout of theschematic layout shown in FIG. 1B and shows the layout different fromFIG. 3. FIG. 4 differs from FIG. 3 with respect to a point that the gateregion SW is not formed into the MOS unit region 103 but the gate regionSW is formed between the FD region 104 and the capacitor region 102. InFIG. 4, since contacts 404 and 403 are similar to the contacts 305 and304 in FIG. 3, their explanation is omitted here.

A contact 402 is arranged in the drain region including the drainterminal of the reset MOS transistor 12 and is used to connect to acontact 401 of the FD region 104. The FD region 104 is also a drainregion including the drain terminal of the first transfer MOS transistor11 and the drain terminal of the second transfer MOS transistor 13. Thatis, in FIG. 4, by using in common the drain region of the first transferMOS transistor 11 and the drain region of the second transfer MOStransistor 13, it is prevented that the capacitance of the FD 17 becomestoo large. There is also such an advantage that by using the layout ofFIG. 4, an area of each pixel can be reduced smaller than that in thelayout of FIG. 3.

An example of the layout different from that of FIG. 4 will now bedescribed. FIG. 5 is a diagram showing the example of the more detailedlayout of the schematic layout shown in FIG. 1B and shows the layoutdifferent from FIG. 4. FIG. 5 differs from FIG. 4 with respect to apoint that the gate region RES of the MOS unit region 103 is arranged insuch a manner that the FD region 104 is used as a drain region and thesource region is used in common with the source-follower MOS transistor15. In FIG. 5, since contacts 412 and 413 are similar to the contacts403 and 404 in FIG. 4, their explanation is omitted here.

A contact 411 in FIG. 5 is used to connect to the gate region SF. Asshown in FIG. 5, the drain regions of the first transfer MOS transistor11, reset MOS transistor 12, and second transfer MOS transistor 13 areused in common. Thus, although the capacitance of the FD 17 increases,since the number of wirings is smaller than that in the case of FIG. 3or 4, a wiring density can be reduced. Consequently, a yield can beimproved. Either the construction in which by using the layout of FIG.5, the improvement of the yield by the reduction in the wiring densityis realized in place of the increase in the capacitance of the FD or theconstruction in which by using the layout of FIG. 3 or 4, the increasein the capacitance of the FD is prevented may be properly selectivelyused in accordance with needs of the user.

Other Embodiments

An embodiment in the case where the solid state image pickup device ineach embodiment mentioned above is applied to a still camera will now bedescribed in detail with reference to FIG. 6.

FIG. 6 is a block diagram showing the case where the solid state imagepickup device in each embodiment mentioned above is applied to the“still camera”.

In FIG. 6, reference numeral 1301 denotes a barrier serving as both of alens protecting device and a main switch; 1302 a lens for focusing anoptical image of an object onto a solid state image pickup device 1304;1303 a diaphragm for varying a quantity of light which passes throughthe lens 1302; 1304 the solid state image pickup device for fetching theobject image formed by the lens 1302 as an image signal; and 1306 an A/Dconverter for converting the analog image signal which is outputted fromthe solid state image pickup device 1304 into digital data.

Reference numeral 1307 denotes a signal processing unit for makingvarious kinds of correction to the image data outputted from the A/Dconverter 1306 or compressing the data; 1308 a timing generator unit foroutputting various timing signals to the solid state image pickup device1304, an image signal processing unit 1305, the A/D converter 1306, andthe signal processing unit 1307; 1309 a whole control arithmeticoperation unit for executing various arithmetic operations andcontrolling the whole still video camera; 1310 a memory unit fortemporarily storing the image data; 1311 an interface unit (I/F unit)for recording or reading out data into/from a recording medium; 1312 adetachable recording medium such as a semiconductor memory or the likeinto/from which the image data is recorded or read out; and 1313 aninterface unit for communicating with an external computer or the like.

The operation of the still video camera in the photographing mode in theforegoing construction will now be described.

When the barrier 1301 is opened, a main power source is turned on, apower source of a control system is subsequently turned on, and further,a power source of photographing system circuits such as an A/D converter1306 and the like is turned on.

After that, to control an exposure amount, the whole control arithmeticoperation unit 1309 opens the diaphragm 1303. The signal outputted fromthe solid state image pickup device 1304 is converted by the A/Dconverter 1306 and subsequently inputted to the signal processing unit1307.

On the basis of the data inputted to the signal processing unit 1307,the whole control arithmetic operation unit 1309 arithmetically operatesthe exposure.

A brightness is discriminated on the basis of a result of a photometryand the whole control arithmetic operation unit 1309 controls thediaphragm in accordance with the discriminated brightness.

On the basis of the signal outputted from the solid state image pickupdevice 1304, the whole control arithmetic operation unit 1309 extractshigh frequency components and arithmetically operates a distance to theobject. After that, the lens is moved and whether or not an in-focusstate has been obtained is discriminated. If it is determined that thein-focus state is not obtained, the lens is driven and a distancemeasurement is performed again.

After the in-focus state is confirmed, the main exposure is started.After the exposure is finished, the image signal outputted from thesolid state image pickup device 1304 is A/D converted by the A/Dconverter 1306. The obtained digital data is transmitted through thesignal processing unit 1307 and written into the memory unit 1310 by thewhole control arithmetic operation unit 1309.

After that, the data stored in the memory unit 1310 is transmittedthrough the recording medium controlling I/F unit 1311 and recorded intothe detachable recording medium 1312 such as a semiconductor memory orthe like under the control of the whole control arithmetic operationunit 1309. It is also possible to construct in such a manner that thedata is transmitted through the external I/F unit 1313 and directlyinputted to a computer or the like and the image is modified.

An embodiment in the case where the solid state image pickup device ineach embodiment mentioned above is applied to a video camera will now bedescribed in detail with reference to FIG. 7.

FIG. 7 is a block diagram showing the case where the solid state imagepickup device in each embodiment mentioned above is applied to the“video camera”. In FIG. 7, reference numeral 1401 denotes aphotographing lens having: a focusing lens 1401A to make a focaladjustment; a zooming lens 1401B to execute the zooming operation; andan image forming lens 1401C.

Reference numeral 1402 denotes a diaphragm; 1403 a solid state imagepickup device for photoelectrically converting an object image formed onan image pickup surface into an electric image signal; and 1404 a sampleand hold circuit (S/H circuit) for sampling and holding the image signaloutputted from the solid state image pickup device 1304, further,amplifying a signal level, and outputting the amplified image signal.

Reference numeral 1405 denotes a process circuit for executingpredetermined processes such as gamma correction, color separation,blanking process, and the like to the video signal outputted from theS/H circuit 1404 and outputting a luminance signal Y and a chroma signalC. The chroma signal C outputted from the process circuit 1405 issupplied to a color signal correcting circuit 1421, by which a whitebalance and a color balance are corrected and color difference signalsR-Y and B-Y are outputted.

The luminance signal Y outputted from the process circuit 1405 and thecolor difference signals R-Y and B-Y outputted from the color signalcorrecting circuit 1421 are modulated by an encoder circuit (ENCcircuit) 1424 and outputted as a standard television signal. Thestandard TV signal is supplied to a video recorder (not shown) or anelectronic view finder such as a monitor EVF (Electric View Finder) (notshown) or the like Reference numeral 1406 denotes an iris controlcircuit for controlling an iris drive circuit 1407 on the basis of thevideo signal supplied from the S/H circuit 1404 and automaticallycontrolling an ig meter 1408 in order to control an aperture amount ofthe diaphragm 1402 so as to set the level of the video signal to apredetermined level value.

Reference numerals 1413 and 1414 denote band pass filters (BPFs) ofdifferent band limitation values each for extracting high frequencycomponents necessary to detect the in-focus state from the video signaloutputted from the S/H circuit 1404. The signals outputted from thefirst band pass filter 1413 (BPF1) and the second band pass filter 1414(BPF2) are gated by a gate circuit 1415 and a focus gate frame signal. Apeak value is detected and held by a peak detecting circuit 1416 andinputted to a logic control circuit 1417. This signal is called a focalvoltage and the focus is set to the in-focus state by the focal voltage.

Reference numeral 1418 denotes a focusing encoder for detecting a movingposition of the focusing lens 1401A; 1419 a zooming encoder fordetecting a focal distance of the zooming lens 1401B; and 1420 an irisencoder for detecting the aperture amount of the diaphragm 1402.Detection values of those encoders are supplied to the logic controlcircuit 1417 to make system control.

The logic control circuit 1417 performs the focal detection to theobject and makes the focal adjustment on the basis of the video signalcorresponding to a portion in a set focal detection region. That is, thelogic control circuit 1417 fetches the peak value information of thehigh frequency components supplied from the BPFs 1413 and 1414, suppliescontrol signals of a rotating direction, rotational speed,rotation/stop, and the like of a focusing motor 1410 to a focus drivecircuit 1409 so as to drive the focusing lens 1401A to a position wherethe peak value of the high frequency components becomes maximum, andcontrol them.

Although the embodiments of the invention have been described in detailabove with reference to the drawings, the specific constructions are notlimited to those of the embodiments but designs and the like in thescope which does not depart from the essence of the invention are alsoincorporated in the invention.

This application claims priority from Japanese Patent Application No.2005-080342 filed on Mar. 18, 2005, which is hereby incorporated byreference herein.

1. A solid state image pickup device comprising a plurality of unitpixels in a matrix shape, in which each of said unit pixels comprises: aphotoelectric conversion unit where carriers are generated by incidentlight; a transfer unit adapted to transfer the carriers; a floatingdiffusion region where the carriers are transferred by said transferunit; a carrier holding unit adapted to accumulate the carriersoverflowed from said photoelectric conversion unit; and an output unitadapted to output a signal corresponding to the carriers transferred tosaid floating diffusion region, wherein one of said carrier holding unitand said output unit is provided between the photoelectric conversionunit included in the first pixel and the photoelectric conversion unitincluded in the second pixel adjacent to the first pixel in the rowdirection, the other one of said carrier holding unit and said outputunit is provided between the photoelectric conversion unit included inthe first pixel and the photoelectric conversion unit included in thethird pixel adjacent to the first pixel in the column direction.
 2. Adevice according to claim 1, wherein said transfer unit and saidfloating diffusion region are arranged between said photoelectricconversion unit and said carrier holding unit.
 3. A device according toclaim 1, wherein said output unit further includes a reset unit adaptedto reset said floating diffusion region.
 4. A device according to claim1, wherein said floating diffusion region and one terminal of saidcarrier holding unit are connected through a switch and said output unitincludes said switch.
 5. A device according to claim 1, wherein saidfloating diffusion region and one terminal of said carrier holding unitare connected through a switch, said switch is arranged between saidphotoelectric conversion unit and said carrier holding unit, and drainregions of said switch and said transfer unit are used in common as saidfloating diffusion region.
 6. A device according to claim 5, wherein adrain region of said reset unit is used in common as said floatingdiffusion region.
 7. A device according to claim 3, wherein saidfloating diffusion region and one terminal of said carrier holding unitare connected through a switch and drain regions of said switch and saidreset unit are used in common.
 8. A device according to claim 1, whereinsaid carrier holding unit which is provided for one side of anapproximate rectangle of said photoelectric conversion unit has a sidelonger than said one side and said output unit which is provided for theother side which crosses said side of said rectangle has a side longerthan said other side.
 9. A camera comprising: a solid state image pickupdevice according to claim 1; a lens adapted to focus an optical image tosaid solid state image pickup device; and a diaphragm adapted to vary aquantity of light which passes through said lens.